Rheostat.



PATENTBD MAR; 24, 1908.

C. D. KNIGHT.

RHEOSTAT. APPLICATION [FILED JULY 18.1907.

3&1 1 2/? Witness 5 6241- 9- 211-:

, to'be operated while at the same time provid- UNITED STATES PATENT OFFICE.

CHARLES D. KNIGHT, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC 2 COMPANY, A CORPORATION OF NEW YORK.

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Specification of Letters Patent.

Patented March 24, 1908.

. Application filed m 18, 1907. Serial No. 384,464.

To all whom it may concern:

Be it known that I, CHARLES D. KNIGHT, a citizen of the 'United States, residing at Schenectady, county of Schenectady',State of New York, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

This invention relates to devices for controlling electric motor circuits and has for its object the provision of a device of this char acter in which the motor will be controlled to a predetermined point in a reliable and simple manner.

My invention relates more specifically to combined starting and speed regulatingrheostats in which the motor is first brought up to running speed and the speed then'varied within certain limits. 7 1

One of the objects of my invention is to providemeans whereby a positive limit is placed upon the speed at which the motor is ing for the variation of this limit. 1 also rovide means Wherebythe setting of the imit is beyond the control of the operator,-

the arrangement being such that the adjusting feature is locked by a key which is not accessible to the operator.

In carrying out my invention Iprovide in connection with starting and speed controlling resistance, a controlling arm which is biased to starting position. A fixed retaining magnet is provided to cooperate with the armature on the controlling arm in the usual way. This armature is made adj ustable and is locked in various ositi-ons by means of a key. In this way t e arm mav be held by the retaining magnet in various positions on the controllingresistance so that a definite speed may not be departed froi In the accompanying drawing, in which I have shown my Invention embodied in a concrete form, Figure 1 is a plan view of the device showing the diagram of circuits; and. Fig. 2 shows the locking device for the ar mature.

Referring to the drawing, 10' is an insulat-- ing base of slate or soapstone provided with a series of contacts 11, forming terminals of starting resistance 12, and a series of contacts 13 for the speed controlling resistance 14. The contacts are concentrically arranged so as to be successively engaged by a controllingjarm 15 pivoted at 16. This arm, is

springressed to the off position, as shown in full lines, by means of the spring 17. A segment 18 is arranged adjacent to contacts 11 and a similar segment 19. is arranged adjacentto contacts 13. -An armature 20 is pivoted to thearm 15 so as to engage the poles of the retaining magnet 21 in-the usual way. The armature instead of being permanently fixed to the arm is made adjustable by being pivoted "to a curved bracket 22 provided with a slot 23. A locking stud or bolt 24 passes through the slot and screws into the arm 15. By tightening this stud the bracket is held in a. fixed position. key or socket wrench 25 is adapted to fit the head of the stud 24 so as to adjust the same.

The arrangement of circuits and the mode of o eration are as follows: When it is desire to start the motor, the arm 15 is moved to the right over the contacts 11- thereby cutting out the resistance, 12. The armature circuit will n'owbe as follows: from the main through the armature A,conductor 26, segment 19, resistance 12 and arm -15 back to the main, the field circuit being com leted from the armature through the field conductor 27 segment 18, arm 15 and back to the main. When the arm passes oil the last stud 11 on to the segment 19, all of the starting resistance is cut out and the motor is running at its lowest speed. By moving the arm farther it passes on to thestuds 13, and the resistance 14 is thereby inserted in the field circuit, increasing the speed of the motor. The movement is continued until the armature 20 engages with the magnet 21 where it is held. By adjusting the armature 20 along the arm, the point at which the the motor must beoperated will be or as shown, and a short-circuiting switch 28 provided for short-circuiting the magnet and stopping the motor .by allowing the controlling arm to go to the off position.

It will be seen that I have provided a very I simple and convenient arrangement whereby the motor may be started and the speed,

varied within certain limits. The speed at which the motorisrun is-taken out of the by Letters Patent of the United States, is-

1. A rheostat for electric motors comprisa resistance, a controlling arm therefor, a retaining magnet for said arm, and an armature for said magnet adjustably mounted upon. the arm. I

A rheostat for electric motors comprising a resistance, a retaining magnet, a controlling arm having an armature cooperating with said magnet, andmeans for locking said 1 armature in various positions on the arm.

3. A rneostat for electric motors comprisin starting resistance and a field resistance, a controlling arm therefor, a retaining magnet for said arm, and an armature for said magnet adjustably mounted upon the -rm.

4. A rheostat for electrio motors comprising a resistance, a controlling arm therefor, a retaining magnet for said arm, an armature for said magnet ad'ustably mounted upon the arm, and a key ior locking the armature in various positions.

5. A rheostat for electric motors comprising a starting resistance and a field resistance, a controlling arm therefor, a retaining magnet for said arm, an armature for said magnet adjustably mounted upon the arm, and a key for locking the arm in various positions.

6. A motor starter comprising starting and field resistance, a spring controlled arm 00- operat-ing therewith, a release magnet responsive to redetermined circuit conditions, and means or retaining the arm in operative relation to the magnet in different positions of field adjustment.

In witness whereof, I have hereunto set my hand this 16th da of Jul 1907.

C ARL is D. KNIGHT.

Witnesses:

HELEN O'aronn, ALEXANDER DtLUNT. 

